It is highly desirable to develop composite aluminum articles having improved resistance to erosion corrosion in aqueous environments due to the wide use of aluminum commercially in aqueous environments. For example, aluminum tubing used in heat exchangers such as aluminum radiators should have a high resistance to erosion corrosion damage by aqueous heat exchange fluid. A particularly suitable composite material is disclosed in U.S. Pat. No. 3,878,871 by the instant inventors and assigned to the assignee of the instant case wherein an aluminum core material consisting essentially of from 0.001 to 0.3% magnesium, 0.2 to 0.8% manganese, 0.001 to 0.1% chromium, 0.001 to 0.2% titanium, 0.05 to 0.5% silicon, 0.001 to 0.2% iron, 0.001 to 0.1% copper, and 0.001 to 0.1% zinc, balance aluminum is metallurgically bonded to an aluminum cladding material consisting essentially of from 0.001 to 0.1% magnesium, 0.8 to 1.2% manganese, 0.001 to 0.1% chromium, 0.001 to 0.1% titanium, 0.001 to 0.05% silicon, 0.001 to 0.05% copper, 0.1 to 0.4% zinc, and 0.001 to 0.1% iron, balance aluminum.
Presently, automobile manufacturers are actively working to substitute aluminum and plastic for brass in various parts of an automobile radiator as a cost and weight saving measure. In some cases, the radiator design calls for a plastic tank to be attached to an aluminum tube assembly so as to form a header. An O-ring gasket is provided between the plastic tank and an aluminum header plate of the aluminum tube assembly so as to provide a leak-free joint. Heretofore, such a design suffered from a distinct disadvantage in that severe crevice corrosion occurred in the groove surface of the aluminum header plate into which the O-ring sealing gasket fits. The crevice corrosion observed was so severe that leakage failures of the radiators occurred in a short time.
In an effort to overcome the above-noted problem, manufacturers provided the aluminum header plate with a sacrificial cladding layer of aluminum alloy 7072. While some improvement in crevice corrosion was observed, it was found that the 7072 alloy dissolved extremely fast and severe crevice corrosion occurred.
Accordingly, it is a principal object of the present invention to provide a triclad aluminum composite having a sacrificial layer which has improved resistance to crevice corrosion in an aqueous environment.
It is a further object of the present invention to provide a triclad aluminum composite particularly suitable as an aluminum header plate in an automobile radiator.
It is still a further object of the present invention to provide an aluminum header plate composed of a triclad composite having a sacrificial clad layer and a brazing clad layer.
Further objects and advantages of the present invention will appear hereinbelow.